Hypoalgesic Effects of Exercise and Training of Different Modalities

Summary

Further research is needed to explore the analgesic effects of post-acute and chronic exercise and if effects are partially dependent on lower H-reflex/V-wave inhibition by group III and IV muscle afferents desensitization. In addition, it is important to note that the available research examining the interaction between exercise (acute and chronic) and pain did not compare the effect of different exercise modalities. Moreover, since discharge rate of III and IV afferents is highly dependent on specific task-metabolic requirements, it is relevant to determine if exercise modality differentially modulates the possible analgesic response via metaboreflex desensitization.

Therefore, with this project, the investigators aim at exploring the influence of experimentally induced metaboreflex activation (group III and IV afferents) (maintained submaximal isometric contraction followed by blood-flow occlusion - post-exercise circulatory occlusion (PECO)) Vs. a control condition (no isometric contraction nor blood flow occlusion), on H-reflex recruitment curve and V-wave excitability (aim #1). Since the activation of group III/IV afferents can inhibit the corticospinal pathway, the investigators hypothesize that the normalized maximal amplitude of H- and V-wave and the slope of the ascending limb of the H-recruitment curve will decrease with metaboreflex activation (during PECO). Additionally, the investigators intend to examine the acute impact of different lower-limb exercise regimens (aerobic, anaerobic and dynamic resistance) on pain sensitivity (by the application of a foot cold pain tolerance test, by determining pressure pain threshold of exercising and non-exercising muscles and through self-reported leg ischemic pain ratings (0-10 Cook scale) - during PECO) (aim #2). Participants are also asked to mark the intensity of cold pain sensation using a visual analogue scale (VAS) with a horizontal line of 100mm, every 30 s of testing.This will allow the investigators to investigate the analgesic role of different acute exercise paradigms through possible metaboreflex desensitization given by altered neuromuscular responses at post-exercise time point (attenuated inhibition of H-reflex and V-wave amplitude during PECO). Also, once past research has shown that muscle metaboreflex activation reduces the sensitivity of the baroreflex, the investigators will measure arterial pressure (AP) and heart rate variability (HRV) during cold test and AP during ischemic testing. Despite all exercise modalities could enhance reducing pain sensibility after exercise, the investigators hypothesize that resistance and anaerobic exercise stimuli will enhance pain threshold/tolerance and reduced pain ratings via metaboreflex desensitization compared to that seen with endurance exercise (attenuated increase of AP and sympathetic component of HRV during cold pressor test and attenuated increase of AP during ischemic pain test). Finally, the investigators intend to explore the impact of long-term aerobic, anaerobic and resistance training on pain sensibility, using the same tests of aim #2 (aim #3). The investigators hypothesize that chronic EIH will be of greater magnitude after anaerobic and resistance exercise training vs. endurance training. This will be related with attenuated inhibition of H-reflex and V-wave amplitude measured during PECO and attenuated increase of AP and sympathetic component of HRV during metaboreflex activation after those training modalities. Nevertheless, the investigators expect to see an increased motor performance in all training regimens via heightened H-reflex (aerobic and anaerobic groups) and V-wave (resistance group) excitability.

Conditions

• Training
• Exercise
• Fatigue
• Occlusion

Interventions

OTHER

Aim #1: The effect of post-exercise circulatory occlusion on H-reflex and V-wave

Aim #1 follows a randomized and crossover design in which 16 young and healthy males are evaluated during thigh circulatory occlusion performed after a submaximal isometric plantar flexion contraction (PECO day). In the other session, participants are evaluated during free-flow conditions and without previous fatiguing contraction (no-PECO day). In PECO day, participants complete a 3-min contraction at 40% of maximal force. Then, for testing, blood flow from lower-leg is blocked during 4 min, by an inflatable cuff around the ipsilateral thigh before task termination, during which H- reflex is tested. At the end of recordings, the cuff is deflated. Participants ware allowed to rest for 5-10 min. Then, they are requested to perform a new 3 min contraction with the cuff being inflated before task termination. The cuff remains inflated for \~ 2 min during which V-wave recordings are obtained. In both days, leg pain intensity is reported by participants and brachial AP is measured.

OTHER

Aim #2: The hypoalgesic effects of acute exercise of different modalities

Aim #2 follows a randomized and crossover-controlled design, consisting on two experimental sessions. 24 healthy male (all diferent from Experiment 1) are randomly allocated to one of the following exercising regimens: aerobic, anaerobic or dynamic resistance (8 participants for each exercise group). In one of the experimental days, participants are evaluated for pain sensitivity and neuromuscular responses both before and after a lower-limb acute exercise protocol (exercise day) and in the other day before and after 15 min of quiet rest (non-exercise day). In both sessions, participants are evaluated for rectus femoris, upper trapezius and biceps brachiis muscles pressure pain threshold, followed by the application of a cold pain tolerance test on the foot. The intensity of pain is reported by a 0-100mm VAS and AP and HRV continously measured. Then, participants are tested for H-reflex and V-wave excitability during PECO, with leg pain intensity (0-10) and brachial AP recorded.

OTHER

Aim #3: The hypoalgesic effects of chronic training of different modalities

Aim #3 follows a randomized-controlled design. 32 healthy male (all the 24 participants from Experimental 2 plus 8 new subjects) are randomly allocated to one of the following groups: aerobic, anaerobic, dynamic resistance training and no-training (control) (8 participants for each group). Each intervention group perform 6 weeks of exercise training (3x week). Participants allocated to each training group are evaluated before and after training (2 assessment days in each time-point). On one day participants are tested for pressure pain threshold and cold pain tolerance with concomitant measures of pain ratings (0-100mm VAS), AP and HRV. The influence of metaboreflex activation on H-reflex and V-wave is also measured (during PECO). In addition, during PECO ischemic pain rating and AP are obtained. On another day, participants are evaluated for motor performance (maximal oxygen uptake, maximal voluntary contraction and peak power) and neuromuscular adaptations (i.e. H-reflex and V-wave)

Sponsors & Collaborators

• Faculdade de Motricidade Humana

  lead OTHER

Principal Investigators

• Gonçalo V Mendonça, PhD · Faculdade de Motricidade Humana

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

NONE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

35 Years

Sex

MALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2022-01-01

Primary Completion

2022-12-30

Completion

2025-05-30

Countries

• Portugal

Study Locations